Unexplained fever with consumptive syndrome in the elderly: two cases of VEXAS syndrome with inflammasome dysregulation.

The aim of this study is to investigate the inflammasome dysregulation in peripheral blood leukocytes of VEXAS patients. The constitutive and in vitro triggered activation of inflammasome in PBMC and neutrophils was analysed in two Brazilian patients with typical UBA1 mutations, and compared with heathy donors. Our findings highlight the constitutive activation of caspase-1 in VEXAS leukocytes, accompanied by increased plasma levels of IL-18. Furthermore, upon stimulation of isolated peripheral blood mononuclear cells (PBMC) and neutrophils, we observed not only the exhaustion of NLRP3 and NLRP1/CARD8 pathways in VEXAS PBMC but also a significant increase in NLRP3-mediated NETs release in VEXAS neutrophils. These findings support previous studies on the contribution of the inflammasome to VEXAS pathogenesis, identifying at least two profoundly affected pathways (NLRP3 and NLRP1/CARD8) in VEXAS peripheral blood.

Cervical carcinoma induces NLRP3 inflammasome activation and IL-1ß release in human peripheral blood monocytes affecting patients’ overall survival

Purpose Our group previously demonstrated that genetic variants in inflammasome genes contribute to protection against the establishment of human papilloma virus (HPV)-associated cervical carcinoma (CC). The objective of this study was to better understand the contribution of inflammasome and its cytokines in the CC microenvironment. Methods The inflammasome activation was analyzed in CC tumoral cell lines and healthy donors (HD)’ monocytes in co-culture. In vitro results were then compared to CC patients’ public databases. Results CC cells did not produce IL-1ß or IL-18 themselves, however, when in co-culture with HD monocytes, induced IL-1ß release in those leucocytes. Inflammasome activation appears to be partially dependent on the NLRP3 receptor. Public data analysis revealed that IL1B expression is increased in the CC compared to normal uterine cervix, and that patients with high IL1B expression had a shorter overall survival. Conclusion CC microenvironment can activate the inflammasome and IL-1ß release in surrounding monocytes, which could be detrimental for CC prognosis (AU)

Canonical Inflammasomes.

The innate immune response represents the first line of host defense, and it is able to detect pathogen- and damage-associated molecular patterns (PAMPs and DAMPs, respectively) through a variety of pattern recognition receptors (PRRs). Among these PRRs, certain cytosolic receptors of the NLRs family (specifically NLRP1, NLRP3, NLRC4, and NAIP) or those containing at least a pyrin domain (PYD) such as pyrin and AIM2, activate the multimeric complex known as inflammasome, and its effector enzyme caspase-1. The caspase-1 induces the proteolytic maturation of the pro-inflammatory cytokines IL-1ß and IL-18, as well as the pore-forming protein gasdermin D (GSDMD). GSDMD is responsible for the release of the two cytokines and the induction of lytic and inflammatory cell death known as pyroptosis. Each inflammasome receptor detects specific stimuli, either directly or indirectly, thereby enhancing the cell's ability to sense infections or homeostatic disturbances. In this chapter, we present the activation mechanism of the so-called "canonical" inflammasomes.

Cervical carcinoma induces NLRP3 inflammasome activation and IL-1ß release in human peripheral blood monocytes affecting patients' overall survival.

PURPOSE: Our group previously demonstrated that genetic variants in inflammasome genes contribute to protection against the establishment of human papilloma virus (HPV)-associated cervical carcinoma (CC). The objective of this study was to better understand the contribution of inflammasome and its cytokines in the CC microenvironment. METHODS: The inflammasome activation was analyzed in CC tumoral cell lines and healthy donors (HD)' monocytes in co-culture. In vitro results were then compared to CC patients' public databases. RESULTS: CC cells did not produce IL-1ß or IL-18 themselves, however, when in co-culture with HD monocytes, induced IL-1ß release in those leucocytes. Inflammasome activation appears to be partially dependent on the NLRP3 receptor. Public data analysis revealed that IL1B expression is increased in the CC compared to normal uterine cervix, and that patients with high IL1B expression had a shorter overall survival. CONCLUSION: CC microenvironment can activate the inflammasome and IL-1ß release in surrounding monocytes, which could be detrimental for CC prognosis.

A common variant close to the "tripwire" linker region of NLRP1 contributes to severe COVID-19.

OBJECTIVE AND DESIGN: The heterogeneity of response to SARS-CoV-2 infection is directly linked to the individual genetic background. Genetic variants of inflammasome-related genes have been pointed as risk factors for several inflammatory sterile and infectious disease. In the group of inflammasome receptors, NLRP1 stands out as a good novel candidate as severity factor for COVID-19 disease. METHODS: To address this question, we performed an association study of NLRP1, DPP9, CARD8, IL1B, and IL18 single nucleotide variants (SNVs) in a cohort of 945 COVID-19 patients. RESULTS: The NLRP1 p.Leu155His in the linker region, target of viral protease, was significantly associated to COVID-19 severity, which could contribute to the excessive cytokine release reported in severe cases. CONCLUSION: Inflammasome genetic background contributes to individual response to SARS-CoV-2.

Severe COVID-19 patients show a dysregulation of the NLRP3 inflammasome in circulating neutrophils.

SARS-CoV-2 triggers inflammasome-dependent release of pro-inflammatory cytokine IL-1ß and pyroptosis, therefore, contributes to the huge inflammatory response observed in severe COVID-19 patients. Less is known about the engagement of inflammasome in neutrophils, main players in tissue injury and severe infection. We studied the activation of the inflammasome in neutrophils from severe COVID-19 patients and assessed its consequence in term of cells contribution to disease pathogenesis. We demonstrated that NLRP3 inflammasome is dramatically activated in neutrophils from severe COVID-19 patients and that the specific inhibition of NLRP3 reverts neutrophils' activation. Next, the stimulation of severe patients' neutrophils with common NLRP3 stimuli was not able to further activate the inflammasome, possibly due to exhaustion or increased percentage of circulating immature neutrophils. Collectively, our results demonstrate that the NLRP3 inflammasome is hyperactivated in severe COVID-19 neutrophils and its exhaustion may be responsible for the increased susceptibility to subsequent (and possibly lethal) infections. Our findings thus include a novel piece in the complex puzzle of COVID-19 pathogenesis.

The Ala134Thr variant in TMEM176B exerts a beneficial role in colorectal cancer prognosis by increasing NLRP3 inflammasome activation.

PURPOSE: TMEM176B was recently described as a negative modulator of Nlrp3 inflammasome activation in mice. In the mouse model, the inhibition of TMEM176B leads to an increased anti-tumoral activity which is dependent on Nlrp3. Since we have recently shown that single nucleotide variants (SNPs) in inflammasome genes, including NLRP3, significantly affect colorectal cancer (CRC) prognosis, we proposed to investigate here the association between genetic variants in TMEM176B and CRC prognosis. METHODS: Considering that, up to now, no genetic study analyzing this gene in humans exists, we selected possible functional SNPs and genotyped them in a cohort of CRC patients submitted to surgery and followed up for more than 10 years. Genotype-guided assays were realized to evaluate the effect of the variant on NLRP3 inflammasome activation. Gene expression from The Cancer Genome Atlas (TCGA) cohort was analyzed to valid possible prognostic and predictive features. RESULTS: We identified the Ala134Thr variant (rs2072443) in TMEM176B as a protective factor for CRC prognosis. This SNP is associated with decreased gene expression and with an increased activation of NLRP3 inflammasome, at least in monocytes and dendritic cells. Furthermore, low TMEM176B expression is associated with higher overall survival. CONCLUSION: Altogether, these findings supported the role of TMEM176B in NLRP3 inflammasome biology and for the first time demonstrated the genetic association between rs2072443 and CRC in humans.

In-vitro NLRP3 functional test assists the diagnosis of cryopyrin-associated periodic syndrome (CAPS) patients: A Brazilian cooperation.

OBJECTIVE: To report our five-years experience on the use of NLRP3 inflammasome functional assays in the differential diagnosis of Brazilian patients with a clinical suspicion of CAPS. PATIENTS AND METHODS: The study included 9 patients belonging to 2 families (I, II) and 7 unrelated patients with a clinical suspicion of AID according to Eurofever/PRINTO classification, recruited between 2017 and 2022. The control group for the NLRP3 functional assay consisted of 10 healthy donors and for the CBA cytokines measurement of 19 healthy controls. Patients underwent clinical evaluation, genetic and functional analysis. RESULTS: All members of the family I received the diagnosis of Muckle-Wells Syndrome (MWS), carried the NLRP3 Thr348Met variant and resulted positive for the functional assay. The 2 patients of the family II resulted negative for the mutational screening but positive for the functional assay compatible with a MWS clinical phenotype. In 2 unrelated patients with NLRP3 mutations, including a novel mutation (Gly309Val, Asp303His), a positive functional test confirmed the clinical diagnosis of NOMID. 3 unrelated MWS and 1 FCAS patients resulted negative to the genetic screening and positive for the functional test. One patient with a FCAS-like phenotype harbored the NLRP12 His304Tyr variant confirming the diagnosis of FCAS2. CONCLUSION: The NLRP3 inflammasome functional assay can assist the clinical diagnosis of CAPS even in patients with unknown genetic defects.

The inflammasomes: crosstalk between innate immunity and hematology.

BACKGROUND: The inflammasome is a cytosolic multi-protein complex responsible for the proteolytic maturation of pro-inflammatory cytokines IL-1ß and IL-18 and of gasdermin-D, which mediates membrane pore formation and the cytokines release, or eventually a lytic cell death known as pyroptosis. Inflammation has long been accepted as a key component of hematologic conditions, either oncological or benign diseases. OBJECTIVES: This study aims to review the current knowledge about the contribution of inflammasome in hematologic diseases. We attempted to depict the participation of specific inflammasome receptors, and the possible cell-specific consequence of complex activation, as well as the use of anti-inflammasome therapies. METHODS: We performed a keyword-based search in public databases (Pubmed.gov, ClinicalTrials.gov.). CONCLUSION: Different blood cells variably express inflammasome components. Considering the immunosuppression associated with both the disease and the treatment of some hematologic diseases, and a microenvironment that allows neoplastic cell proliferation, inflammasomes could be a link between innate immunity and disease progression, as well as an interesting therapeutic target.

The genetics behind inflammasome regulation.

The inflammasome is a cytosolic multiproteic complex that promotes proinflammatory events through the release of the cytokines IL-1ß and IL-18, and in some context by the induction of a lytic cell death called pyroptosis, in response to damage, infections, or changes in the homeostasis. Due to the powerful inflammatory effect, there are several regulatory mechanisms that are essential to modulate or limit the activation of the inflammasome. When these mechanisms fail, the deregulation of the complex leads or contributes to the development of a plethora of diseases characterized by constitutive and/or chronic inflammation, such as autoinflammatory, autoimmune, cardiovascular, neurodegenerative, and metabolic diseases, cancer, or even severe complications of infectious diseases. Either environmental or genetic factors may affect the threshold and/or the level of inflammasome activation, such as hyperglycemia, hyperuricemia, auto-antibodies, unfolded proteins and fibrils, or individual genetic variants in genes coding for inflammasome receptors or effector molecules, and also in regulators. While the genetics of inflammasome itself has been elsewhere characterized and also recently reviewed by our group, less is known about how genetic variants in regulatory molecules could affect inflammatory diseases. Therefore in this work, we selected a group of known or possible regulators of the inflammasome, and through the review of genetic association studies we tried to depict the contribution of these regulators in the development of multifactorial diseases.

Genetic contribution and functional impairment of inflammasome in sickle cell disease.

BACKGROUND: Sickle cell disease (SCD), one of the most common single-gene disorders, is caused by mutations in the hemoglobin ß-chain gene. Clinical presentation is heterogeneous, and inflammation is a common condition. Thereby, we hypothesized that inflammasome and related cytokine IL-1ß could represent significant SCD pathogenesis contributors. MATERIAL AND METHODS: 161 SCD (SS/Sß) patients were enrolled for the study. Seven single nucleotide polymorphisms (SNPs) in 5 inflammasome genes (NLRP1, NLRP3, NLRC4, CARD8, IL1B) were selected based on minor allele frequency. Total peripheral blood mononuclear cells (PBMC) and monocytes were isolated from 10 out of 161 SCD patients (HbSS) and 10 healthy donors (control group, Ctrl) for inflammasome analysis. RESULTS: SCD patients presented a functional impairment of inflammasome, with monocytes and peripheral blood mononuclear cells (PBMC) exhibiting a different NLRP3 inflammasome activation rate. Gain-of-function variants in NLRP1 and IL1B genes resulted associated with a mild SCD clinical presentation. DISCUSSION: Our results can contribute to the understanding of SCD inflammation. SCD patients showed possible exhaustion of monocytes due to chronic inflammation, moreover others cells in PBMC can contribute to the NLRP3 inflammasome activation. NLRP1 gain-of-function was associated with mild clinical presentation, suggesting that other inflammasome receptors can be involved in SCD. This is the first study reporting a significant contribution of inflammasome SNPs in SCD.

Recessive NLRC4-Autoinflammatory Disease Reveals an Ulcerative Colitis Locus.

PURPOSE: NLRC4-associated autoinflammatory disease (NLRC4-AID) is an autosomal dominant condition presenting with a range of clinical manifestations which can include macrophage activation syndrome (MAS) and severe enterocolitis. We now report the first homozygous mutation in NLRC4 (c.478G > A, p.A160T) causing autoinflammatory disease with immune dysregulation and find that heterozygous carriers in the general population are at increased risk of developing ulcerative colitis. METHODS: Circulating immune cells and inflammatory markers were profiled and historical clinical data interrogated. DNA was extracted and sequenced using standard procedures. Inflammasome activation assays for ASC speck formation, pyroptosis, and IL-1ß/IL-18 secretion confirmed pathogenicity of the mutation in vitro. Genome-wide association of NLRC4 (A160T) with ulcerative colitis was examined using data from the IBD exomes portal. RESULTS: A 60-year-old Brazilian female patient was evaluated for recurrent episodes of systemic inflammation from six months of age. Episodes were characterized by recurrent low-grade fever, chills, oral ulceration, uveitis, arthralgia, and abdominal pain, followed by diarrhea with mucus and variable skin rash. High doses of corticosteroids were somewhat effective in controlling disease and anti-IL-1ß therapy partially controlled symptoms. While on treatment, serum IL-1ß and IL-18 levels remained elevated. Genetic investigations identified a homozygous mutation in NLRC4 (A160T), inherited in a recessive fashion. Increased ASC speck formation and IL-1ß/IL-18 secretion confirmed pathogenicity when NLRC4 (A160T) was analyzed in human cell lines. This allele is significantly enriched in patients with ulcerative colitis: OR 2.546 (95% 1.778-3.644), P = 0.01305. CONCLUSION: NLRC4 (A160T) can either cause recessively inherited autoinflammation and immune dysregulation, or function as a heterozygous risk factor for the development of ulcerative colitis.

NLRP1 acts as a negative regulator of Th17 cell programming in mice and humans with autoimmune diabetes.

Type 1 diabetes (T1D) is an autoimmune disease characterized by the destruction of pancreatic ß cells. We show here that the protein NOD-like receptor family pyrin domain containing 1 (NLRP1) has a key role in the pathogenesis of mouse and human T1D. More specifically, downregulation of NLRP1 expression occurs during T helper 17 (Th17) differentiation, alongside greater expression of several molecules related to Th17 cell differentiation in a signal transducers and activators of transcription 3 (STAT3)-dependent pathway. These changes lead to a consequent increase in interleukin 17 (IL-17) production within the pancreas and higher incidence of diabetes in streptozotocin (STZ)-injected mice. Finally, in patients with T1D and a SNP (rs12150220) in NLRP1, there is a robust decrease in IL-17 levels in serum and in memory Th17 cells from peripheral blood mononuclear cells. Our results demonstrate that NLRP1 acts as a negative regulator of the Th17 cell polarization program, making it an interesting target for intervention during the early stages of T1D.

Common pathogen-associated molecular patterns induce the hyper-activation of NLRP3 inflammasome in circulating B lymphocytes of HIV-infected individuals.

OBJECTIVE: Despite the antiretroviral treatment, people with HIV (PWH) still experience systemic chronic inflammation and immune-senescence, which represent risk factors for severe comorbidities and inefficient response to pathogens and vaccines. Given the dysregulation of NLRP3 inflammasome in PWH and the recently demonstrated role played by NLRP3 in B lymphocytes, we hypothesized that NLRP3 dysregulation in B cells can contribute to chronic inflammation and humoral dysfunction in PWH. DESIGN: NLRP3 inflammasome activation was evaluated in B lymphocytes and correlated with antibodies production and immunization response in PWH. METHODS: NLRP3 inflammasome activation was compared in B lymphocytes isolated from PWH and healthy donors, in resting and stimulated conditions. Functional polymorphic variants in NLRP3 and IL1B genes were analysed in a cohort of PWH submitted to anti-HBV vaccine to assess the effect of NLRP3 inflammasome on humoral response. RESULTS: The NLRP3 inflammasome activation in response to common PAMPs (LPS, ß-glucan) resulted higher in B lymphocytes of PWH than in HD. CpG-induced IgM secretion was also increased in B cells of PWH. NLRP3, but not IL1B, gain-of-function polymorphism associated to anti-HBs levels. CONCLUSION: These data reveal the dysregulation of NLRP3 inflammasome in B lymphocytes of PWH. Differently from myeloid compartment, which present an exhausted NLRP3 inflammasome, the complex appears to be hyper-activated in B cells of PWH, likely contributing to chronic inflammation and affecting humoral response.

Single-Nucleotide Variants in the AIM2 - Absent in Melanoma 2 Gene (rs1103577) Associated With Protection for Tuberculosis.

Tuberculosis (TB) remains a serious public health burden worldwide. TB is an infectious disease caused by the Mycobacterium tuberculosis Complex. Innate immune response is critical for controlling mycobacterial infection. NOD-like receptor pyrin domain containing 3/ absent in melanoma 2 (NLRP3/AIM2) inflammasomes are suggested to play an important role in TB. NLRP3/AIM2 mediate the release of pro-inflammatory cytokines IL-1ß and IL-18 to control M. tuberculosis infection. Variants of genes involved in inflammasomes may contribute to elucidation of host immune responses to TB infection. The present study evaluated single-nucleotide variants (SNVs) in inflammasome genes AIM2 (rs1103577), CARD8 (rs2009373), and CTSB (rs1692816) in 401 patients with pulmonary TB (PTB), 133 patients with extrapulmonary TB (EPTB), and 366 healthy control (HC) subjects with no history of TB residing in the Amazonas state. Quantitative Real Time PCR was performed for allelic discrimination. The SNV of AIM2 (rs1103577) is associated with protection for PTB (padj: 0.033, ORadj: 0.69, 95% CI: 0.49-0.97). CTSB (rs1692816) is associated with reduced risk for EPTB when compared with PTB (padj: 0.034, ORadj: 0.50, 95% CI: 0.27-0.94). Serum IL-1ß concentrations were higher in patients with PTB than those in HCs (p = 0,0003). The SNV rs1103577 of AIM2 appeared to influence IL-1ß release. In a dominant model, individuals with the CC genotype (mean 3.78 ± SD 0.81) appeared to have a higher level of IL-1ß compared to carriers of the T allele (mean 3.45 ± SD 0.84) among the patients with PTB (p = 0,0040). We found that SNVs of AIM2 and CTSB were associated with TB, and the mechanisms involved in this process require further study.

Inflammatory effect of Bothropstoxin-I from Bothrops jararacussu venom mediated by NLRP3 inflammasome involves ATP and P2X7 receptor.

Muscle tissue damage is one of the local effects described in bothropic envenomations. Bothropstoxin-I (BthTX-I), from Bothrops jararacussu venom, is a K49-phospholipase A2 (PLA2) that induces a massive muscle tissue injury, and, consequently, local inflammatory reaction. The NLRP3 inflammasome is a sensor that triggers inflammation by activating caspase 1 and releasing interleukin (IL)-1ß and/or inducing pyroptotic cell death in response to tissue damage. We, therefore, aimed to address activation of NLRP3 inflammasome by BthTX-I-associated injury and the mechanism involved in this process. Intramuscular injection of BthTX-I results in infiltration of neutrophils and macrophages in gastrocnemius muscle, which is reduced in NLRP3- and Caspase-1-deficient mice. The in vitro IL-1ß production induced by BthTX-I in peritoneal macrophages (PMs) requires caspase 1/11, ASC and NLRP3 and is dependent on adenosine 5'-triphosphate (ATP)-induced K+ efflux and P2X7 receptor (P2X7R). BthTX-I induces a dramatic release of ATP from C2C12 myotubes, therefore representing the major mechanism for P2X7R-dependent inflammasome activation in macrophages. A similar result was obtained when human monocyte-derived macrophages (HMDMs) were treated with BthTX-I. These findings demonstrated the inflammatory effect of BthTX-I on muscle tissue, pointing out a role for the ATP released by damaged cells for the NLRP3 activation on macrophages, contributing to the understanding of the microenvironment of the tissue damage of the Bothrops envenomation.

Sensing soluble uric acid by Naip1-Nlrp3 platform.

Uric acid (UA), a product of purine nucleotide degradation able to initiate an immune response, represents a breakpoint in the evolutionary history of humans, when uricase, the enzyme required for UA cleavage, was lost. Despite being inert in human cells, UA in its soluble form (sUA) can increase the level of interleukin-1ß (IL-1ß) in murine macrophages. We, therefore, hypothesized that the recognition of sUA is achieved by the Naip1-Nlrp3 inflammasome platform. Through structural modelling predictions and transcriptome and functional analyses, we found that murine Naip1 expression in human macrophages induces IL-1ß expression, fatty acid production and an inflammation-related response upon sUA stimulation, a process reversed by the pharmacological and genetic inhibition of Nlrp3. Moreover, molecular interaction experiments showed that Naip1 directly recognizes sUA. Accordingly, Naip may be the sUA receptor lost through the human evolutionary process, and a better understanding of its recognition may lead to novel anti-hyperuricaemia therapies.

Macrophage inflammatory state in Type 1 diabetes: triggered by NLRP3/iNOS pathway and attenuated by docosahexaenoic acid.

Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease characterized by insulin-producing pancreatic ß-cell destruction and hyperglycemia. While monocytes and NOD-like receptor family-pyrin domain containing 3 (NLRP3) are associated with T1D onset and development, the specific receptors and factors involved in NLRP3 inflammasome activation remain unknown. Herein, we evaluated the inflammatory state of resident peritoneal macrophages (PMs) from genetically modified non-obese diabetic (NOD), NLRP3-KO, wild-type (WT) mice and in peripheral blood mononuclear cells (PBMCs) from human T1D patients. We also assessed the effect of docosahexaenoic acid (DHA) on the inflammatory status. Macrophages from STZ-induced T1D mice exhibited increased inflammatory cytokine/chemokine levels, nitric oxide (NO) secretion, NLRP3 and iNOS protein levels, and augmented glycolytic activity compared to control animals. In PMs from NOD and STZ-induced T1D mice, DHA reduced NO production and attenuated the inflammatory state. Furthermore, iNOS and IL-1ß protein expression levels and NO production were lower in the PMs from diabetic NLRP3-KO mice than from WT mice. We also observed increased IL-1ß secretion in PBMCs from T1D patients and immortalized murine macrophages treated with advanced glycation end products and palmitic acid. The present study demonstrated that the resident PMs are in a proinflammatory state characterized by increased NLRP3/iNOS pathway-mediated NO production, up-regulated proinflammatory cytokine/chemokine receptor expression and altered glycolytic activity. Notably, ex vivo treatment with DHA reverted the diabetes-induced changes and attenuated the macrophage inflammatory state. It is plausible that DHA supplementation could be employed as adjuvant therapy for treating individuals with T1D.

Inflammatory effect of Bothropstoxin-I from the Bothrops jararacussu venom mediated by NLRP3 inflammasome involves ATP and P2X7 receptor

Muscle tissue damage is one of the local effects described in bothropic envenomations. Bothropstoxin-I (BthTX-I), from B. jararacussu venom, is a K49-phospholipase A2 that induces a massive muscle tissue injury, and, consequently, local inflammatory reaction. The NLRP3 inflammasome is a sensor that triggers inflammation by activating caspase 1 and releasing IL-1b and/or inducing pyroptotic cell death in response to tissue damage. We, therefore, aimed to address activation of NLRP3 inflammasome by BthTX-I-associated injury and the mechanism involved in this process. Intramuscular injection of BthTX-I results in infiltration of neutrophils and macrophages in gastrocnemius muscle, which is reduced in NLRP3- and Caspase-1-deficient mice. The in vitro IL-1β production induced by BthTX-I- inperitoneal macrophages requires caspase 1/11, ASC and NLRP3 and is dependent of ATP-induced K+ efflux and P2X7R. BthTX-I induces a dramatic release of ATP from C2C12 myotubes, therefore representing the major mechanism for P2X7R-dependent inflammasome activation in macrophages. A similar result was obtained when human monocyte-derived macrophages were treated with BthTX-I. These findings demonstrated the inflammatory effect of BthTX-I on muscle tissue, pointing out a role for the ATP released by damaged cells for the NLRP3 activation on macrophages, contributing to the understanding of the microenvironment of the tissue damage of the Bothrops envenomation.

Macrophage inflammatory state in Type 1 diabetes: triggered by NLRP3/iNOS pathway and attenuated by docosahexaenoic acid

Type 1 diabetes mellitus (T1D) is a chronic autoimmune disease characterized by insulin-producing pancreatic β-cell destruction and hyperglycemia. While monocytes and NOD-like receptor family-pyrin domain containing 3 (NLRP3) are associated with T1D onset and development, the specific receptors and factors involved in NLRP3 inflammasome activation remain unknown. Herein, we evaluated the inflammatory state of resident peritoneal macrophages (PMs) from genetically modified non-obese diabetic (NOD), NLRP3-KO, wild-type (WT) mice and in peripheral blood mononuclear cells (PBMCs) from human T1D patients. We also assessed the effect of docosahexaenoic acid (DHA) on the inflammatory status. Macrophages from STZ-induced T1D mice exhibited increased inflammatory cytokine/chemokine levels, nitric oxide (NO) secretion, NLRP3 and iNOS protein levels, and augmented glycolytic activity compared to control animals. In PMs from NOD and STZ-induced T1D mice, DHA reduced NO production and attenuated the inflammatory state. Furthermore, iNOS and IL-1β protein expression levels and NO production were lower in the PMs from diabetic NLRP3-KO mice than from WT mice. We also observed increased IL-1β secretion in PBMCs from T1D patients and immortalized murine macrophages treated with advanced glycation end products and palmitic acid. The present study demonstrated that the resident PMs are in a proinflammatory state characterized by increased NLRP3/iNOS pathway-mediated NO production, up-regulated proinflammatory cytokine/chemokine receptor expression and altered glycolytic activity. Notably, ex vivo treatment with DHA reverted the diabetes-induced changes and attenuated the macrophage inflammatory state. It is plausible that DHA supplementation could be employed as adjuvant therapy for treating individuals with T1D.